1. Field of the Invention
The present invention relates to a method of signal processing applied to a Multi-Input/Multi-Output (MIMO) system, and more particularly to a signal processing method by which a data stream is transmitted selectively using only some of a plurality of available transmitting antennas or weight vectors based on channel quality information for each transmitting antenna.
2. Background of the Related Art
A V-BLAST (Vertical Bell Laboratories Layered Space Time) system is one example of a MIMO system, which includes M transmitting antennas and N receiving antenna (where N≧M). See, for example, P. W. Wolniansky, G. J. Foschini, G. D. Golden and R. A. Valenzuela, ‘V-BLAST: An Architecture for Realizing Very High Data Rates over the Rich-scattering Wireless Channel’, IEE Electronics Letters, Vol. 35, No. 1, pp. 14-16, January, 1999, which is hereby incorporated in its entirety.
In more detail, by transmitting different signals in parallel over different antennas, in an environment characterized by rich scattering and multipath, this technique can provide high data rates thanks to an efficient algorithm on the receiving end which includes interference nulling from yet undetected signals and interference cancellation from already detected signals. In this manner, the receiver is able to produce independent virtual subchannels, one for each transmitting antenna, leading to a channel capacity which grows approximately linearly with the number of antennas. However, an increase in the number of transmitting antennas also increases the amount of channel quality information fed back to the transmitting end from the receiving end. The overhead requirements for processing the channel quality information and the interference caused by excessive channel quality information negatively effects the overall system performance.